Effect of particle breakage on the shear strength of calcareous sands

Houzhen Wei,Tao Zhao,Ke Yan,Mei Yin,Jianhua Shen,Qingshan Meng,Xinzhi Wang,Jianqiao He

doi:10.1007/s11001-021-09440-2

Abstract

The particle breakage of calcareous sands plays a key role in determining the particle shape and shear strength. This process has been analysed in the current study by employing the ring shear tests on calcareous sands sampled from the South China Sea. In this study, a set of parameters, e.g. roundness and aspect ratio, have been employed to quantify the geometrical properties of calcareous sands pre- and after the breakage. These two parameters have been found to correlate well with the vertical loading stress level, shear strain and shear strength. The particle breakage leads to the change of micro-structure during the shear test, as illustrated by the Scanning Electron Microscopy (SEM) images. It is found that during the shearing deformation, particle breakages can effectively reduce, while particle rearrangements can increase the shear strength of the calcareous sands.

Highlights

Calcareous sands can be widely observed in tropical marine environment
The residual shear strength decreased with increasing roundness and aspect ratio, which illustrated the strong effect of particle breakage on the residual shear strength
Some conceptual models were proposed to explain the effect of particle breakage on the change in shear strength by investigating the mechanical properties, fracture characteristics and particle shape characteristics of calcareous sands, and the following main conclusions have been obtained: (1) At the beginning of shearing, both the roundness and aspect ratio of the calcareous sand particles reduced significantly, so surfaces of the particles tended to be smooth and rounded

Summary

Introduction

Calcareous sands can be widely observed in tropical marine environment. The intrinsic properties distinguish calcareous sands from other terrigenous sediments both physically and mechanically, in terms of particle angularity, high crushability, and weakly cemented soil structure (Wang et al 2017). The material composition (e.g. mainly calcium carbonate of low hardness) together with particle morphology such as angularity, surface roughness, as an inherent feature of soil have significant influence on its mechanical and geological properties (e.g. shear strength, dilatancy and crushability). Owing to these unique properties, calcareous sands can be fragmented readily under even relatively low loading stress (Wei et al 2018).

Methods

Results

Discussion

Conclusion